Fecal specimens for different tests often need different transport containers and different transport conditions (eg, frozen, raw stool). Specimens should be portioned out to separate devices of each type for each test requested before sending to the laboratory. Stool for bacterial culture and enterohemorrhagic E. coli Shiga toxin by EIA should be submitted in the C&S transport vial. Only a thumbnail size portion of stool, about 1 g or 1 mL, should be added to the vial. Overfilling the vial will reduce recovery of stool pathogens.
Specimens from sources, such as genital, stool, urine, upper and lower respiratory specimens, cannot be cultured under the aerobic bacterial culture test number. If specimens are incorrectly submitted with an order for aerobic bacterial culture, the laboratory will process the specimen for the test based on the source listed on the request form. The client will not be telephoned to approve this change, but the change will be indicated on the report.
Studies have shown that patients who did not have gastroenteritis or other GI symptoms on admission are unlikely to have diarrheal illness due to Salmonella, Shigella, Campylobacter, or enterohemorrhagic E. coli.
Stool: Specimen should be collected in sterile bedpan, not contaminated with urine, residual soap, or disinfectants. Those portions of stool which contain pus, blood, or mucous should be transferred to sterile specimen container.
Rectal swab: Pass swab beyond anal sphincter, carefully rotate, and withdraw. Swabbing of lesions of rectal wall or sigmoid colon during proctoscopy or sigmoidoscopy is preferred.
Duodenal or sigmoid aspirate: Specimen should be collected by a physician trained in this procedure.
Stool specimen can be divided for other types of cultures by laboratory. Miscellaneous tests and ova and parasites tests should be split into appropriate containers and transport prior to shipping to laboratory.
Indications for stool culture include:1
Diarrhea is common in patients with the acquired immunodeficiency
syndrome (AIDS). It is frequently caused by the classic bacterial
pathogens as well as unusual opportunistic bacterial pathogens and
parasitic infestation. (Giardia, Cryptosporidium, and
Entamoeba histolytica frequently reported.) Cryptosporidium
and Pneumocystis can occur with AIDS. Rectal swabs are useful for
the diagnosis of Neisseria gonorrhoeae and Chlamydia
infections. AIDS patients are also subject to cytomegalovirus,
Salmonella, Campylobacter, Shigella, C. difficile,
herpes, and Treponema pallidum gastrointestinal tract
In acute or subacute diarrhea, three common syndromes are recognized: gastroenteritis, enteritis, and colitis (dysenteric syndrome). With colitis, patients have fecal urgency and tenesmus. Stool are frequently small in volume and contain blood, mucus, and leukocytes. External hemorrhoids are common and painful. Diarrhea of small bowel origin is indicated by the passage of few large volume stools. This is due to accumulation of fluid in the large bowel before passage. Leukocytes indicate colonic inflammation rather than a specific pathogen. Bacterial diarrhea may be present in the absence of fecal leukocytes and fecal leukocytes may be present in the absence of bacterial or parasitic agents (ie, idiopathic inflammatory bowel disease).2 See table. Although most bacterial diarrhea is transient (1-30 days) cases of persistent symptoms (10 months) have been reported. The etiologic agent in the reported case was Shigella flexneri diagnosed by culture of rectal swab.3 In infants younger than 1 year of age, a history of blood in the stool, more than 10 stools in 24 hours, and temperature greater than 39°C have a high probability of having bacterial diarrhea.4,5 Diarrhea is also a common side effect of long term antibiotic treatment. Although often associated with Clostridium difficile, other bacteria and yeasts have been implicated.